Optical integrator rods are well known components used primarily in illumination systems for electronic projectors. An optical integrator rod is a hollow or solid internally reflective “light pipe” that uses multiple reflections of a focused light source to obtain homogenization of round or irregular patterns of illumination and convert them into a uniform rectangular pattern. This pattern can be imaged onto a panel such as an LCD (Liquid Crystal Display) or DMD (Digital Micromirror Device) by a relay lens system, and then projected to a screen. Thus, the optical integrator rod is used to improve uniformity and efficiently match the aspect ratio of the illumination source to the panel.
There are two basic types of reflective integrators: a “tunnel” type made of four mirrors, and a solid glass integrator or “solid rod integrator”. This latter type is more efficient than the former since it works on lossless multiple reflections using TIR (the Total Internal Reflection) of the glass rod.
Traditionally, for a dual lamp projection system separate integrators have been used for each lamp. Light from each lamp is focused orthogonally onto the input face of the associated integrator rod, and collected at the output face thereof for transmission to the relay lens. Examples of prior systems are disclosed in U.S. Pat. No. 6,196,699 (Stanton), U.S. Pat. No. 6,341,876 (Moss et al), U.S. Pat. No. 6,527,420 (Chuang), U.S. Pat. No. 6,857,761 (Chang), U.S. Pat. No. 6,488,379 (Kane).
The inventor has recognized the desirability of replacing separate integrator rods for each lamp with a single rod, in order to benefit from advantages such as simple mounting, simple alignment, less coupling loss, lower cost since there is no need to provide a mirror coating (only AR coating is required), and eliminated risk of high power damage on the mirror coating.